Doctor Yellow Test Train to Be Retired as Shinkansen with New Tech to Take Over Rail Inspections

Two different views of the inside of a Doctor Yellow train are seen in Tokyo in 2024.
10:36 JST, February 3, 2025
Doctor Yellow Shinkansen trains have long served railway safety by testing tracks and overhead wires on the Tokaido and Sanyo Shinkansen lines. One of the two trains in operation just retired in January.
Although aging is one of the main reasons for the test trains’ retirement, Doctor .Yellow have also become obsolete for reasons such as the emergence of faster trains. Now, the latest technologies such as AI are being used in inspection vehicles.
Wave of faster trains

Doctor Yellow trains are formally called Shinkansen electric track comprehensive inspection cars. They have supported the safety of Japan’s main transportation artery since the opening of the Tokaido Shinkansen in 1964.
Generally, inspection and construction vehicles for conventional lines are painted yellow so that they can be easily recognized at night, thus preventing accidents. Doctor Yellow trains have also been yellow since the first-generation (T1) model used when the line opened.
Since they are not commercial trains, their operating schedules are irregular and not made public. For that reason, it is said that seeing a Doctor Yellow train brings good luck, making them popular with people of all ages.
As of the end of last year, the third-generation or T4, introduced in 2001, and the T5, introduced in 2005, ran between Tokyo and Hakata stations about once every 10 days. During each trip, eight inspectors spent two days checking about 70 items, including buckling of tracks and wear on the wiring. The T4 retired in January, and the T5 will be retired sometime after 2027.
Both the T4 and T5 were made based on the 700 series Shinkansen that stopped being manufactured in the 2000s and was retired from the Tokaido Shinkansen Line in 2020. The third-generation trains are aging and cannot carry the latest equipment because the series’ technology has become obsolete.
Speed is another reason for Doctor Yellow’s retirement. The current Tokaido Shinkansen bullet trains have a maximum speed of 285 kph, while Doctor Yellow can reach 270 kph, which is not fast enough to run between the gaps in the high-speed train operation schedule.
Introduction of AI
Trains with higher top speeds are fundamentally changing the way inspections are conducted. Instead of using test trains, a system has already been introduced in which operational trains automatically check for abnormalities in the wires and tracks while in service.
Since 2022, the latest N700S train series, which operate as Nozomi Shinkansen trains, have been fitted with dedicated inspection equipment. They can shine beams of infrared light onto wires from their roofs to check for wear and tear, or check the current of the automatic train control (ATC) signals running through rails.
The next-generation train car, which is under development to be introduced in 2027 or later, will have additional function to automatically detect abnormalities in wire fittings, rails and sleepers. It will have a higher testing capacity than Doctor Yellow. Point cloud data and AI-assisted image diagnosis technology will also be introduced to reduce the burden on inspectors while improving inspection accuracy.
Evolving conventional lines
Aside from Shinkansen line, systems and inspection cars that make use of big data and AI have been developed for conventional lines, too.
Since 2020, West Japan Railway Co. (JR West) runs a condition monitoring system on some of its trains, which constantly collects and stores data on the electrical system, air pressure, interior temperature and other conditions. Data on the vehicles and equipment that previously was checked only during regular inspections is now automatically collected at a high frequency and stored on its inspection department’s cloud to allow for a quick detection to vehicle damage.
JR West also introduced an app in October last year which automatically assesses the status of the cars’ functions based on the accumulated data. It predicts the deterioration of devices and determines the appropriate timing for repairs.
The DEC741, JR West’s comprehensive inspection train which has been operated on conventional lines since 2021, is equipped with more than 50 cameras on its roof. It currently undergoes a proving test to detect problems by photographing electrical equipment such as utility poles and traffic lights while traveling at speeds of 100 kph. In the past, the job was done by workers, and the train’s introduction is expected to greatly reduce labor.
In August last year, the DEC741 was upgraded to be able to photograph rail fasteners and other track equipment and equipped with an AI-based image diagnosis system. The change cut the necessary number of visual confirmations that must be done in person by half.
Robots for hazardous work


Two different views of the inside of a Doctor Yellow train are seen in Tokyo in 2024.
When inspections find defects in aboveground facilities such as the tracks or wiring, maintenance workers are dispatched to do repairs. However, this always puts the workers’ lives at risk, as trains are constantly passing on the tracks and a high-voltage current flows through the wiring.
According to the Health, Labor and Welfare Ministry’s industrial accident statistics, 11 people died in industrial accidents on the railroads and tramways between 2019 and 2023. In addition, fatal accidents have also occurred involving workers from partner companies, with two workers from outside JR West being killed during maintenance work in fiscal 2023, including one dying from electric shock.
Maintenance workers on site have complained that they were not provided with sufficient safety equipment. Therefore, a robot has been brought in to do dangerous tasks.
In July, JR West installed a humanoid robot mounted on a 14-ton truck-type work vehicle that can run on the railway tracks. The robot has two arms that can hold up to 40 kilograms and trim trees growing near the tracks. Workers wear virtual reality goggles and operate the robot from the control room in the back of the truck.
The machine is expected to help reduce the risk of injury from blades, falls and electric shock, as well as improve work efficiency. Previously, three workers were required to watch and assist, but the machinery reduces the number to two.
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